On Thu, 2010-10-28 at 01:25 -0700, Nicholas A. Bellinger wrote: > On Thu, 2010-10-28 at 04:21 -0400, Jeff Garzik wrote: > > On 10/28/2010 03:01 AM, Nicholas A. Bellinger wrote: > > > Following yet another round of convincing discussions from jgarzik and jejb > > > this afternoon, this RFCv8 patch series follows their recommendation and does a > > > SCSI subsystem wide 'push down' of struct Scsi_Host->host_lock usage from > > > scsi_dispatch_cmd() into legacy LLDs that require (or we are not sure about) > > > the host_lock held while SHT->queuecommand() I/O dispatch occurs. > > > > Great! > > > > > > > diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c > > > index d050e07..672a8c9 100644 > > > --- a/drivers/ata/libata-scsi.c > > > +++ b/drivers/ata/libata-scsi.c > > > @@ -3174,7 +3174,7 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, > > > * ATA and ATAPI devices appearing as SCSI devices. > > > * > > > * LOCKING: > > > - * Releases scsi-layer-held lock, and obtains host lock. > > > + * None > > > * > > > * RETURNS: > > > * Return value from __ata_scsi_queuecmd() if @cmd can be queued, > > > @@ -3190,7 +3190,6 @@ int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *)) > > > > > > ap = ata_shost_to_port(shost); > > > > > > - spin_unlock(shost->host_lock); > > > spin_lock(ap->lock); > > > > > > ata_scsi_dump_cdb(ap, cmd); > > > @@ -3204,7 +3203,6 @@ int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *)) > > > } > > > > > > spin_unlock(ap->lock); > > > - spin_lock(shost->host_lock); > > > return rc; > > > } > > > > > > > This is not an equivalent transformation, because we just lost _irqsave > > and _irqstore. > > > > You might want to double-check to ensure this problem is not replicated > > in other non-legacy drivers. > > Understood, so for libata this will need to turn into the equivilent > spin_lock_irqsave() + spin_unlock_irqrestore() for ap->lock, right..? > > So apart from libata that leaves the following LLDs running in host_lock > less mode: > > drivers/infiniband/ulp/iser/iscsi_iser.c: Running in host_lock less mode (libiscsi) > drivers/message/fusion/mptscsih.c: Running in host_lock less mode (internal) > drivers/message/fusion/mptfc.c: Running in host_lock less mode (internal) > drivers/message/fusion/mptsas.c: Running in host_lock less mode (internal) > drivers/message/fusion/mptspi.c: Running in host_lock less mode (internal) > drivers/scsi/aic94xx/aic94xx_init.c: Running in host_lock less mode (libsas) > drivers/scsi/be2iscsi/be_main.c: Running in host_lock less mode (libiscsi) > drivers/scsi/bnx2i/bnx2i_iscsi.c: Running in host_lock less mode (libiscsi) > drivers/scsi/fnic/fnic_main.c: Running in host_lock less mode (internal) > drivers/scsi/iscsi_tcp.c: Running in host_lock less mode (libiscsi) > drivers/scsi/lpfc/lpfc_scsi.c: Running in host_lock less mode (internal) > drivers/scsi/mpt2sas/mpt2sas_scsih.c: Running in host_lock less mode (internal) > drivers/scsi/mvsas/mv_init.c: Running in host_lock less mode (libsas) > drivers/scsi/pm8001/pm8001_init.c: Running in host_lock less mode (libsas) > drivers/scsi/qla2xxx/qla_os.c: Running in host_lock less mode (internal) > drivers/scsi/qla4xxx/ql4_os.c: Running in host_lock less mode (internal) > drivers/scsi/scsi_debug.c: Running in host_lock less mode (internal) > drivers/scsi/cxgbi/cxgb3i/cxgb3i.c: Running in host_lock less mode (libiscsi) > drivers/scsi/cxgbi/cxgb4i/cxgb4i.c: Running in host_lock less mode (libiscsi) > > I will take another look and make sure any LLD specific locks that are > obtained in SHT->queuecommand() from the host_lock-less drivers are > assuming they need to call internal locks with _irqsave + _irqrestore > held and include these into lio-4.0.git/host_lock-less-for-37-v9. > Ok, so originally libiscsi, fnic, and lpfc where using spin_unlock(host->host_lock) -> spin_lock(host->host_lock) And libsas, qla2xxx, qla4xxx where using spin_unlock_irq(host->host_lock) -> spin_lock_irq(host->host_lock) Just to verify, you are thinking that those *not* using spin_unlock_irq + spin_lock_irq() for the legacy optimization dispath should have their per LLD host lock converted to spin_lock_irqsave() + spin_unlock_irqrestore(), right..? --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
